#include <stdio.h>

void exchange (int* a, int* b)
{
	int num = 0;
	num = *a;
	*a = *b;
	*b = num;
}

int main()
{
	int a = 10;
	int b = 30;
	printf("%d\n%d\n", a, b);
	exchange (&a, &b);
	printf("%d\n%d\n", a,b);
	return 0;
}